Production of silicon quantum dots for photovoltaic applications by picosecond pulsed laser ablation

Semiconductor nanocrystals exhibiting strong quantum confinement effects have been produced by picosecond pulsed laser ablation. Crystalline, nanometer-sized Si particles with average sizes ranging from one to five nanometers were collected on both crystalline and glassy substrates. Nanoparticle size can be tuned through variation of the laser pulse energy density and by distance of the collection area from the plume center. Raman spectra of the particles confirm the crystalline nature of the nanoparticles and exhibit significant shifts due to phonon confinement effects. Optical absorption spectra of Si nanoparticles show absorption onsets ranging from 1.7 eV to 3.0 eV. These properties, combined with relatively narrow measured size distributions, make these quantum dots excellent candidates for inclusion in nanocomposite solar cells.